The invention relates to gas turbine engines, and more particularly, to a fan drive gear system for gas turbine engines.
One type of gas turbine engine includes a fan drive gear system that couples turbo-machinery of the engine with the fan. Typical turbo-machinery includes two axially extending concentric shafts. The two shafts rotate at different speeds and couple the high pressure compressor with the high pressure turbine and the low pressure compressor with the low pressure turbine. Typically, one of the shafts (typically the low rotor shaft) additionally drives the fan, via the fan drive gear system. The fan acts to compress and move air through a nacelle of the gas turbine engine. In this manner, a substantial portion of the thrust of the gas turbine engine is generated.
Fan drive gear systems may utilize an epicyclic gear train which includes a sun gear that is driven by the low rotor shaft, planet gears which are circumferentially arranged about and intermesh with the sun gear and a ring gear that is disposed about and intermeshes with the planet gears. Depending upon the configuration, either the planet gears or the ring gear rotationally drive the fan in response to rotation of the sun gear.
Typically in epicyclic gear trains each planet gear is supported on and rotates relative to one journal bearing. Each journal bearing extends between and is supported at either axial end by a carrier. The carrier is bolted to a torque frame, which is secured to a fixed structure or rotating structure depending upon the particular configuration of the gear system.
Unfortunately, the configuration of the carrier (supporting the journal bearings at either end) and the dense high strength alloys typically used for the carrier contributes unwanted weight to the gas turbine engine.